Background: The international classification of diseases version 10 (ICD-10) uses alphanumeric expanded codes and external cause of injury codes (E-codes).
Objective: To examine the reliability and validity of emergency department (ED) coders in applying E-codes in ICD-9 and -10.
Methods: Bicycle and pedestrian injuries were identified from the ED information system from one period before and two periods after transition from ICD-9 to -10 coding. Overall, 180 randomly selected bicycle and pedestrian injury charts were reviewed as the reference standard (RS). Original E-codes assigned by ED coders (ICD-9 in 2001 and ICD-10 in 2004 and 2007) were compared with charts (validity) and also to ICD-9 and -10 codes assigned from RS chart review, to each case by an independent (IND) coder (reliability). Sensitivity, specificity, simple, and chance-corrected agreements (κ statistics) were calculated.
Results: Sensitivity of E-coding bicycle injuries by the IND coder in comparison with the RS ranged from 95.1% (95% CI 86.3 to 99.0) to 100% (95% CI 94.0 to 100.0) for both ICD-9 and -10. Sensitivity of ED coders in E-coding bicycle injuries ranged from 90.2% (95% CI 79.8 to 96.3) to 96.7% (95% CI 88.5 to 99.6). The sensitivity estimates for the IND coder ranged from 25.0% (95% CI 14.7 to 37.9) to 45.0% (95% CI 32.1 to 58.4) for pedestrian injuries for both ICD-9 and -10.
Conclusion: Bicycle injuries are coded in a reliable and valid manner; however, pedestrian injuries are often miscoded as falls. These results have important implications for injury surveillance research.